Optical gratings are used in a wide variety of optical applications such as monochromators, spectrometers, wavelength division multiplexing, and various optical storage technologies. An optical grating is a periodic structure that diffracts light in multiple directions. One way to form an optical grating is to create a number of slits into a structure. This type of optical grating is referred to as a transmissive grating. Another way to form an optical grating is to create small regions of reflective material. This type of optical grating is referred to as a reflective grating.
An incident plane wave of light onto an optical grating structure will cause the light coming out of the structure to behave as a light source at either the slits or reflective regions. For example, with a reflective grating, the light being reflected off of the grating will behave as if the reflective material was a light source. Thus, the light being reflected will disperse in all directions. The angle of the incident light as well as the spacing between the narrow slits or reflective regions will affect the manner in which the grating system disperses the light.
An optical grating is typically a static structure. This is because the manner in which the optical grating disperses light is dependent upon the physical characteristics of the grating material. To affect the manner in which an optical grating system disperses light, the physical formation of the grating must be altered.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.